Reporter: The motive for the murder of colorado prison chief mike clements may have been revenge for breaking up a prison gang. Clements, concerned about the rise of a white supremacist's group, 211 crew, sent its leaders to another prison, trying to diminish their powerbase. Suspected gunman, 28-year-old evan ebel, just paroled in january, was a member of 211 crew. Law enforcement have yet to publicly confirm the connection. Fear tonight -- the potential for more attacks from other gang members. Abc news has learned the colorado state prisons have been put on a modified lockdown, as a security precaution until at least monday. The governor's mansion and state capitol have expanded security, following the murder. Prison gangs are prolific across america. The american correctional association reports almost 14% of the prison population are involved in gangs. An estimated 200,000 inmates. Investigators believe ebel may be linked to other murders. There's physical evidence in that car we want to try to recover and then compare to see whether or not we are on track at the crime scenes in colorado. Reporter: A law enforcement source says they are not convinced that evan ebel acted alone, looking into whether he had an accomplice. A public memorial is scheduled

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